1-[N2-((S)-ethoxycarbonyl)-3-phenylproply)-N6-trifluoroacetyl]-L-ysyl-L-proline (lisinopril (TFA) ethyl ester, LPE)

ABSTRACT

A method of isolating 1-[N 2 -((S)-ethoxycarbonyl)-3-phenylpropyl)-N 6 -trifluoroacetyl]-L-lysyl-L-proline (lisinopril (TFA) ethyl ester, LPE). The solvent or solvent mixture used for the extraction is also a main constituent of the solvent or solvent mixture from which the crystallization takes place. High yield as well as good purity of the end product are obtained, without distillation. 1-[N 2 -((S)-ethoxycarbonyl)-3-phenylpropyl)-N 6 -trifluoroacetyl]-L-lysyl-L-proline (lisinopril (TFA) ethyl ester, LPE) is described as a precursor for producing an ACE inhibitor.

CROSS REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 08/951,579, filed Oct. 16,1997, now U.S. Pat. No. 5,907,004.

This application claims priority from German Application No. 19732839.3,filed on Jul. 30, 1997, the subject matter of which is herebyincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a method of isolating1-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(LPE, compound I).

BACKGROUND OF THE INVENTION

N-substituted amino acids of this type are valuable intermediateproducts for the production of inhibitors of angiotensin-convertingenzyme (ACE), which act as regulators of blood pressure. The compound offormula (I) is the direct intermediate product for1-[N²-((S)-carboxy)-3-phenylpropyl)]-L-lysyl-L-proline (Lisinopril II),which exhibits superb therapeutic results in combating high bloodpressure (Zestril®, Coric®, Prinivil®).

Compound (I) is obtained according to the state of the art by thereductive amination of 2-oxo-4-phenyl-ethyl butyrate with the dipeptideLys (Tfa)-Pro.

Such a method is described in the J. Org. Chem. 1988, 53, pp. 836-844.According thereto, compound (I) is obtained in a yield of 42% by basicextraction of the raw reaction solution, a subsequent extraction of theproduct in methylene chloride at pH 4.6 and, after a change of solvent,crystallization from methyl-tert.butyl ether, cyclohexane.

EP 05 23 449 concerns the synthesis of compound (I) obtained accordingto example 3 with a yield of 60%. The workup of the raw reactionsolution obtained according to this method contains, in addition to thebasic and an acidic extraction step with 1,1,1-trichloroethane, acrystallization from methyl-tert.-butyl ether.

In principle, other methods for producing compound (I) are also knownwhich are not based on reductive amination but are less advantageous (EP0 336 368 A2). The aqueous product phase is extracted therein withmethylene chloride. However, after drying of the organic phase oversodium sulfate the solvent is again changed for crystallization inmethyl-tert.-butyl ether.

The crystallization from pure methyl-tert.-butyl ether results in acrystal grain which is difficult to filter and in yields which arefrequently insufficient (EP 0 645 398 A1). If compound (I) is allowed tocrystallize out of solutions with a high concentration an additionalrecrystallization becomes necessary. The addition of cyclohexane (J.Org. Chem., 1988, 53, pp. 836-844) during the crystallization forincreasing the yield is also described. However, there is the danger ofa separation as oil, which makes it much more difficult to isolate theproduct, not only on an industrial scale.

EP 0 645 398 A1 extensively examines the possibility of thecrystallization of compound (I) from various solvents or solventmixtures. It is shown therein that when methyl-tert.-butyl ether ormixtures containing methyl-tert.-butyl ether are used the residualsolvent content of the crystals is very great after the crystallizationand residual solvent is bound in the crystal. The LPE raw materialobtained in this manner is extremely difficult to dry. Long drying timeswhich can adversely affect the product quality (formation of DKP,especially at elevated temperatures) and the tendency of the product toagglutinate makes special, expensive drying procedures necessary.

WO 95/07928 teaches a type of workup which describes an extraction withsubsequent crystallization. The raw material of the LPE production ispre-cleaned in a pH range of 0-6.3, if necessary by means of severalliquid/liquid extraction steps before it is crystallized out of amixture of methyl-tert.-butyl ether and methyl cyclohexane at reducedtemperatures. A solvent exchange also takes place between the extractionand the crystallization.

A disadvantage of the methods of the state of the art for working up LPEis the fact that frequently environmentally hazardous chlorinatedsolvents are used and the solvent must be replaced during the workup.This is difficult to achieve completely on an industrial scale and as aresult of which only insufficiently defined solvent compounds can beadjusted for the crystallization. In addition, only mild temperatureconditions are permitted for such solvent changes on account of thesensitivity of the product, which entails long distillation times.Moreover, the methods of the state of the art often result in crystalswhich are difficult to filter and much residual solvent is includedtherewith. Such a product requires long drying procedures which make itdifficult to control caking and agglutination on an industrial scale.

SUMMARY OF THE INVENTION

In view of the state of the art indicated and discussed herein, theinvention therefore has the purpose of finding a novel method forisolating LPE (I) which permits the raw material obtained from an LPEproduction process to be better isolated from an aqueous product phasewith a simplified and more economic process, which for its part helpsreduce the customary long drying times which stress the LPE (I) and morefavorable crystalline properties of the precipitated material areobtained.

The invention also has the purpose of generating an end LPE materialusing the novel, simpler isolating methods which end material isimproved over that of the state of the art with comparable drying times,especially as concerns the residual solvent content.

The invention also has the purpose of providing an improved LPE (I)

As a result of the fact that LPE (I) is extracted with a solvent orsolvent mixture from an aqueous product solution of an LPE productionprocess produced according to the method of the state of the art andthat this solvent or solvent mixture is subsequently used as a maincomponent of the solvent or solvent mixture from which the LPE (I) iscrystallized, crystals of LPE distinguished by more advantageouscrystalline properties are obtained by this simplified and much moreeconomic method. The LPE generated in this manner exhibits only slightsolvent inclusion after crystallization and possesses excellentfilterability on account of its well-formed crystalline structure. Theslight amount of included residual solvent is a reason that the previouslong drying times per drying batch can be significantly reduced. The LPEproduced in this manner has a byproduct content which is just asexcellently low as that of the state of the art. Thus, a product whichis more advantageous in comparison to the state of the art cansurprisingly be produced in spite of the simplified method of extractionand crystallization of LPE, which is a reason that a more cost-effectivemethod for the production of LPE can be made available.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows, graphically, x-ray diffraction reflexes of LPE (I) of theprior art.

FIG. 2 shows, graphically, x-ray diffraction reflexes of LPE (I) of thesubject invention.

DETAILED DESCRIPTION OF THE INVENTION

It is especially advantageous if the novel method for the extraction andcrystallization of LPE (I) is carried out with solvents or solventmixtures consisting of esters and/or ketones of the general formula(III)

which solvents or solvent mixtures can be additionally mixed, ifnecessary, with open-chain aliphatic or cycloaliphatic hydrocarbons assolvent.

The groups R₁ and R₂ therein advantageously stand for a group of (C₁-C₆)alkyl groups. These groups can be linear or branched. In particular, thegroups can contain: methyl, ethyl, n-propyl, isopropyl, n-butyl,sec-butyl, isobutyl, tert.-butyl, n-pentyl, n-hexyl. Group R₂ comprisesthe group of group R, and also the group of the (C₁-C₆) alkoxy groups.The latter can also be linear or branched. The following are, inparticular, suitable for R₂: methoxy, ethoxy, n-propoxy, isopropoxy,n-butoxy, sec-butoxy, isobutoxy, tert.-butoxy, n-pentoxy, n-hexoxy. Themixing of the solvent or solvent mixture with the hydrocarbons can becarried out before or even after the extraction. These hydrocarbons areopen-chain aliphatic hydrocarbons which contain 5-9 C atoms. They can belinear or branched as desired. “Cycloaliphatic hydrocarbons” denotesrings having 5 to 7 C atoms which can be substituted as desired with(C₁-C₄) alkyl groups which can be present in branched form. Thefollowing have proven to be quite especially advantageous solvents andsolvent mixtures:

Esters—Ethyl acetate, n-propyl acetate, n-butyl acetate, ethylpropionate

Ketones—Methyl isobutyl ketone, diethyl ketone, methyl isopropyl ketone

Aliphatics—n-pentane, n-hexane, cyclohexane, methyl cyclohexane.

Higher homologs of the solvents described above are also suitable, witha natural boundary resulting on account of the rising boiling points andtherewith a deterioration of the drying properties of the moistcrystallizate. Any combination of the above-named, especiallyadvantageous solvents have proven to be especially advantageous solventmixtures.

These solvents and/or solvent mixtures can also be used with advantagefor pre-cleaning the aqueous product phase at a pH between 0 and 3.5.This pre-cleaning takes place before the actual extraction of the LPE(I) in the organic phase, and has the result that the aqueous productphase includes few byproducts. Since the same solvents and/or solventmixtures can be used which can also be used for the extraction andcrystallization, the necessity of making available additional storagecapacity for solvents and/or solvent mixtures which differ from those ofthe extraction and crystallization of the LPE (I) is advantageouslyreduced. Likewise, this clearly improves the possibility of recyclingthe solvents. It is consequently always especially advantageous in anindustrial process to use as few different solvents as possible.

In addition, an advantageous embodiment of the method can be seen inthat an activated carbon purification can be carried out in the same pHrange of 0-3.5 after the solvent treatment described above but beforethe actual extraction of the LPE (I) into an organic solvent or solventmixture. This again clearly improves the ability of the LPE (I) to becrystallized.

The extraction of the LPE (I) described above from its aqueous productphase is subsequently carried out in a pH range between 3.5 and 6.3,especially preferably 3.9 to 4.8. It is quite especially preferred thatthe organic solution of LPE (I) obtained in this manner is washed beforethe crystallization with water at a pH of 4.8 to 6.3—a range of 5.7 to6.0 is especially preferred—and that the aqueous phase is separated fromthe organic phase.

According to the invention the LPE extraction solution can beazeotropically dehydrated before the concluding crystallization, ifnecessary by distillation. The indicated solvents and solvent mixturesfunction thereby as water-entraining medium.

The extraction steps discussed above are advantageously carried out at atemperature between 0° C. and 60° C., preferably at 20° C. to 50° C. andespecially preferably at 35° C. to 45° C. If solvent mixtures are usedvolumetric ratios between esters and/or ketones and thealiphatic/cycloaliphatic hydrocarbons used of between 1:0.01 and 1:100,quite especially advantageously 1:0.5 to 1:2 are used. The concludingcrystallization takes place according to the invention at temperaturesbetween−40° C. and +50° C. After the crystallization an aliphatic orcycloaliphatic hydrocarbon like that already described in detail abovecan be added with advantage once more, optionally after the motherliquor has been evaporated to low bulk, to the latter. This results in anew crystallization during which the yields of >75% of LPE (I) whichwere already high in the past can be increased again by approximately10%.

The present invention also comprises a novel LPE (I) distinguished by anovel and advantageous crystal modification. LPE (I) produced accordingto the prior state of the art exhibits a completely different X-raydiffraction behavior than one obtained according to the presentinvention. Significant new, different reflexes in an X-ray diffractionof the novel LPE (I) in a transmission diffractometer manufactured bySTOE/Darmstadt are shown in Table 1.

TABLE 1 No. 2 Theta 1  6.7241 2  9.4851 3 11.9034 4 16.3074 5 17.8722

Diffractometer:Transmission

Monochromator:Curved Ge (111)

Wavelength:1.540598 Cu

Detector:Curved PSD

Scan mode:Transmission/stationary PSD/fixed omega

2Theta scan

The reflexes shown in Table 1 have a relative intensity of ≧30% of themain reflex at 21.2663. The tolerance of the 2Theta values is maximally±10%. A deviation of ±5% is preferred and the uncertainty is quiteespecially preferred at ±1%. However, errors of not greater than ±0.02units usually occur in apparatus which has been properly adjusted andcalibrated.

FIGS. 1 and 2 contrast the X-ray diagrams of two LPE specimens. FIG. 1shows the reflexes of an LPE (I) produced according to the state of theart (method according to EP 0 719 279, comparative Example 1, completelydried product). FIG. 2 shows results from a specimen obtained accordingto Example 8 of the present invention. However, all X-ray diagrams ofthe specimens of examples 2-10 show equal reflex distributions and equalrelative intensities.

This novel crystal modification has the result that the LPE (I) can befiltered especially well.

According to the invention the drying times of the LPE (I) produced inthis manner are significantly below those of the state of the art. Thefinding of the novel crystal modification was therewith causal for thepossibility of being able to carry out the LPE production method in aneconomically more advantageous manner.

The following non-limiting examples are intended to clarify theinvention.

Comparative Example 11-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 120 ml toluene and 30 mlethyl acetate the pH was adjusted with concentrated hydrochloric acidto 1. The mixture was then agitated for 10 min. and the phasessubsequently separated. A pH of 4 was now adjusted at 5° C. in theaqueous phase and the latter extracted with 400 ml ethyl acetate. Thephases were separated, the organic phase mixed with 110 ml water andadjusted with sodium hydroxide solution (50%) to a pH of 5.8. Afterphase separation the organic phase was largely evaporated to low bulk ina vacuum at max. 33° C. bottom temperature. The bottom was mixed with125 ml toluene and evaporated further to low bulk to 120 g. Thereafter,240 ml methyl-tert.-butyl ether were added and cooled down to +4° C. Acrystalline precipitate was produced thereby. To this crystallinesuspension, 50 ml methyl cyclohexane were added dropwise at 4° C. within3 h. The mixture was then agitated 1 h, filtered, washed andsubsequently dried in an oil pump vacuum 4 h at RT.

Yield: 67.7 g (85.2% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 92.0 (+−0.4)n.d. 6400 toluene −24.0 49100 methyl-tert- dibutyl ether 770 methylcyclohexane (n.d. = not determined)

EXAMPLE 2 1-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 120 ml toluene and 30 mlethyl acetate the pH was adjusted with concentrated hydrochloric acidto 1. The mixture was then agitated for 10 min. and the phasessubsequently separated. A pH of 4 was now adjusted at 40° C. in theaqueous phase and the latter extracted with 450 ml ethyl acetate. Thephases were separated, the organic phase mixed with 110 ml water andadjusted with sodium hydroxide solution (50%) to a pH of 5.8. Afterphase separation. 235 ml methyl cyclohexane were added to the organicphase and evaporated to low bulk in a vacuum at max. 40° C. bottomtemperature to 290 g. The bottom was cooled down to −5° C. A crystallineprecipitate was produced which was filtered, washed and subsequentlydried in an oil pump vacuum 4 h at RT.

Yield: 48.0 g (60.5% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 98.3 (+−0.3)85-90 n.n. ethyl acetate −25.2 126 methyl cyclohexane (n.n. = cannot bedemonstrated)

EXAMPLE 31-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 120 ml toluene and 30 mlethyl acetate the pH was adjusted with concentrated hydrochloric acidto 1. The mixture was then agitated for 10 min. and the phasessubsequently separated. A pH of 4 was now adjusted at 40° C. in theaqueous phase and the latter extracted with 450 ml ethyl propionate. Thephases were separated, the organic phase mixed with 110 ml water andadjusted with sodium hydroxide solution (50%) to a pH of 5.8. Afterphase separation 225 ml methyl cyclohexane were added to the organicphase and evaporated to low bulk in a vacuum at max. 40° C. bottomtemperature to 270 g. The bottom was mixed with 250 ml methylcyclohexane and cooled down to +5° C. A crystalline precipitate wasproduced which was filtered, washed and subsequently dried in an oilpump vacuum 4 h at RT.

Yield: 59.9 g (75.4% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 96.8 (+−0.8)87-90 <20 −25.5 ethyl propionate- 598 methyl cyclohexane

EXAMPLE 41-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 120 ml toluene and 30 mlethyl acetate the pH was adjusted with concentrated hydrochloric acidto 1. The mixture was then agitated 10 min and the phases subsequentlyseparated. A pH of 4 was now adjusted at 40° C. in the aqueous phase andthe latter extracted with 450 ml n-propyl acetate. The phases wereseparated, the organic phase mixed with 110 ml water and adjusted withsodium hydroxide solution (50%) to a pH of 5.8. After phase separation300 ml n-hexane were added to the organic phase and evaporated to lowbulk in a vacuum at max. 40° C. bottom temperature to 240 g. The bottomwas mixed with 206 ml n-hexane and cooled down to +5° C. A crystallineprecipitate was produced which was filtered, washed and subsequentlydried in an oil pump vacuum 4 h at RT.

Yield: 54.8 g (69% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 97.0 (+−0.6)87-91 <20 n-propyl −25.4 acetate 43 n-hexane

EXAMPLE 51-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 120 ml toluene and 30 mlethyl acetate the pH was adjusted with concentrated hydrochloric acidto 1. The mixture was then agitated 10 min. and the phases subsequentlyseparated. A pH of 4 was now adjusted at 40° C. in the aqueous phase andthe latter extracted with 450 ml ethyl propionate. The phases wereseparated, the organic phase mixed with 110 ml water and adjusted withsodium hydroxide solution (50%) to a pH of 5.8. After phase separationthe organic phase was evaporated to low bulk in a vacuum at max. 40° C.bottom temperature to 230 g. The bottom was mixed with 275 mlcyclohexane and cooled down to +5° C. A crystalline precipitate wasproduced which was filtered, washed and subsequently dried in an oilpump vacuum 4 h at RT.

Yield: 60.0 g (75.6% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 97.4 (+−0.8)87-91 <20 ethyl −25.3 propionate 524 cyclohexane

EXAMPLE 61-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 120 ml toluene and 30 mlethyl acetate the pH was adjusted with concentrated hydrochloric acidto 1. The mixture was then agitated 10 min. and the phases subsequentlyseparated. A pH of 4 was now adjusted at 40° C. in the aqueous phase andthe latter extracted with 450 ml n-propyl acetate. The phases wereseparated, the organic phase mixed with 110 ml water and adjusted withsodium hydroxide solution (50%) to a pH of 5.8. After phase separationthe organic phase was evaporated to low bulk in a vacuum at max. 40° C.bottom temperature to 200 g. The bottom was mixed with 270 mlcyclohexane and cooled down to +5° C. A crystalline precipitate wasproduced which was filtered, washed and subsequently dried in an oilpump vacuum 4 h at RT.

Yield: 56.5 g (71.2% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 97.6 (+−0.2)87-91 <20 propyl −25.4 acetate 253 cyclohexane

EXAMPLE 71-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 120 ml toluene and 30 mlethyl acetate the pH was adjusted with concentrated hydrochloric acidto 1. The mixture was then agitated 10 min. and the phases subsequentlyseparated. A pH of 4 was now adjusted at 40° C. in the aqueous phase andthe latter extracted with 450 ml methyl isobutyl ketone. The phases wereseparated, the organic phase mixed with 110 ml water and adjusted withsodium hydroxide solution (50%) to a pH of 5.8. After phase separationthe organic phase was evaporated to low bulk in a vacuum at max. 40° C.bottom temperature to 230 g. The bottom was mixed with 185 ml methylcyclohexane and cooled down to +5° C. A crystalline precipitate wasproduced which was filtered, washed and subsequently dried in an oilpump vacuum 4 h at RT.

Yield: 56.1 g (70.6% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 97.6 (+−0.6)87-91 91 methyl isobutyl −25.5 ketone 253 methyl cyclohexane

EXAMPLE 81-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 120 ml toluene and 30 mlethyl acetate the pH was adjusted with concentrated hydrochloric acidto 1. The mixture was then agitated 10 min. and the phases subsequentlyseparated. A pH of 4 was now adjusted at 40° C. in the aqueous phase andthe latter extracted with 450 ml methyl isobutyl ketone. The phases wereseparated, the organic phase mixed with 110 ml water and adjusted withsodium hydroxide solution (50%) to a pH of 5.8. After phase separationthe organic phase was evaporated to low bulk in a vacuum at max. 40° C.bottom temperature to 185 g. The bottom was mixed with 235 mlcyclohexane and cooled down to +5° C. A crystalline precipitate wasproduced which was filtered, washed and subsequently dried in an oilpump vacuum 4 h at RT.

Yield: 60.5 g (76.2% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 98.4 (+−0.5)87-91 207 methyl isobutyl −25.4 ketone 226 cyclohexane

EXAMPLE 91-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously to Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 45 ml methyl isobutyl ketoneand 45 ml cyclohexane the pH was adjusted with concentrated hydrochloricacid to 1. The mixture was then agitated 10 min. and the phasessubsequently separated. A pH of 4 was now adjusted at 40° C. in theaqueous phase and the latter extracted with 450 ml methyl isobutylketone. The phases were separated, the organic phase mixed with 110 mlwater and adjusted with sodium hydroxide solution (50%) to a pH of 5.8.After phase separation the organic phase was evaporated to low bulk in avacuum at max. 40° C. bottom temperature to 185 g. The bottom was mixedwith 235 ml cyclohexane and cooled down to +5° C. A crystallineprecipitate was produced which was filtered, washed and subsequentlydried in an oil pump vacuum 4 h at RT.

Yield: 61 g (76.8% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 98.6 (+−0.4)87-91 215 methyl isobutyl −25.6 ketone 280 cyclohexane

EXAMPLE 101-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(compound I)

A reductive amination according to patent application EP 05 23 449 iscarried out analogously in Example 3, page 10.

Workup

The reaction solution, for which the dosage for the workup was selectedin such a manner that in addition to the typical byproduct profilealtogether 150 mmol of the desired LPE-(SSS)-diastereomer (I) were init, was largely concentrated by evaporation in a vacuum at 45° C. bathtemperature. The residue was taken up in 1400 ml water and brieflystripped in a vacuum. After the addition of 45 ml methyl isobutyl ketoneand 45 ml cyclohexane the pH was adjusted with concentrated hydrochloricacid to 1. The mixture was then agitated 10 min. and the phasessubsequently separated. A pH of 4 was now adjusted at 40° C. in theaqueous phase and the latter extracted with 450 ml methyl isobutylketone. The phases were separated, the organic phase mixed with 110 mlwater and adjusted with sodium hydroxide solution (50%) to a pH of 5.8.After phase separation the organic phase was evaporated to low bulk in avacuum at max. 40° C. bottom temperature to 160 g. The bottom was mixedwith 175 ml cyclohexane and cooled down to +5° C. A crystallineprecipitate was produced thereby. To this crystalline suspension, 103ml. cyclohexane was added dropwise at 5° C. within 1.5 hr. The mixturewas then agitated for 1 hr., filtered, washed and subsequently dried inan oil pump vacuum 4 h at RT.

Yield: 66.0 g (83.1% of theoretical)

Analytics

(α)25/D SSS diastereomer (c = 1 MeOH/ content Melting point Residualsolvent 0.IN HCl) (% by weight) (° C.) (mg/kg) (degrees) 97.4(+−0.3)87-91 167 methyl isobutyl −25.6 ketone 218 cyclohexane

What is claimed is: 1.1-[N²-((S)-ethoxycarbonyl)-3-phenylpropyl)-N⁶-trifluoroacetyl]-L-lysyl-L-proline(LPE) of formula (I)

with reflexes at 6.7241 9.4851 11.9034 16.3073 17.8722 (2 theta), andhaving no individual organic solvent present at a residual level greaterthan 598 mg/kg, said residual level being determined after the LPE hasdried for 4 h in an oil pump vacuum at room temperature.
 2. LPE offormula (I)

produced from an aqueous solution in an LPE production process byextraction and subsequent crystallization, comprising using a solvent orsolvent mixture, excluding methyl tert, butyl ether, to extract the LPEof formula (1) which solvent or solvent mixture is also a mainconstituent of a solvent or solvent mixture used for the crystallizationwherein the crystallization step yields LPE of formula (1) with reflexesat 6.7241 9.4851 11.9034 16.3073 17.8722 (2 theta), and having noindividual organic solvent present at a residual level greater than 598mg/kg, said residual level being determined after the LPE has dried for4 h in an oil pump vacuum at room temperature.